A similiar situation to this is the swastika. If you are not Jewish, you may not feel it as strongly as you feel about the SC flag, but it is exactly the same for anyone who was persecuted by the Nazis, which also included Roma, Catholics, homosexuals, and political prisoners. The swastika in ancient times had a positive connotation, but it was the Nazis who, with their actions, turned the positive to the negative, so negative that to show a swastika now creates the same, perhaps even more violently negative reactions in people. If you were German and supported the Nazis (one finds it hard to believe that was possible but it was), then the swastika was a symbol of your heritage.